1. Field of the Invention
This invention generally relates to a signal conversion circuit and method, and more particularly, to a circuit and method for improving mismatches caused by signal converters, reference voltage generators and clock generators.
2. Description of the Related Art
Analog signals have the characteristics of being interfered with easily and being difficult to save; therefore, the analog signals will be generally converted to digital signals through AD converters before they are transmitted or saved. When the digital signals are received from a receiver or read from a storage device, the digital signals will be converted back to analog signals through DA converters. A display system 10, as shown in FIG. 1, includes a video apparatus 11, e.g. a personal computer or a DVD player, a video processor 12 and a display device 13. There are several converter stages that exist in the display device 10, including AD converters and DA converters. The video signals, in a display system, which will be converted by the converters, include red, green and blue video signals; therefore, at least three converters are needed for each converter stage so as to respectively convert the three color video signals.
For a circuit designer, in order to have three converters, used in the same system, matched with each other, the other two converter circuit structures are duplicated from an original converter circuit structure designed by the designer so as to improve mismatches between the three converters to the smallest level, as shown in FIG. 2. FIG. 2 shows a block diagram of a conventional signal conversion circuit 20 including three converters 21, 22 and 23 therein, and each converter includes a clock generator, a reference voltage generator and a conversion unit. However, due to limitations by the fabrication process, even circuit structures designed to be identical still have problem of mismatches therebetween, such as timing skew that exists between same designed clock generators; voltage differences existing between same designed reference voltage generators; and mismatches existing between same designed conversion units. These are the so-called “mismatches” between converters. Therefore, mismatches still exist between the aforementioned converter stages.
One conventional method for solving the aforementioned mismatch problems between converters is done by means of calibration, as shown in FIG. 3. This may comprise performing color calibration of the display system after its integrated circuits have be manufactured, e.g. adjusting bias shift or clock shift of the converters. Another method is to utilize additional circuits implemented in the integrated circuit to calibrate converters so as to compensate mismatches therebetween. However, this will increase manufacturing cost.
According to the above reasons, it is necessary to further improve aforementioned converters such that mismatches between converters can be eliminated and the circuit structure can be simplified.